2.5" iirc mate, I was answering you when I said its a Good exhaust lol Yeah this is Socks old one, although unfortunately between his ownership and the lad I bought it off, the bracket which attaches this Exhaust to the car hangers(fujitsubos had a bracket which bolted onto the cars chassis then attached to the exhaust with standard style hangers) went missing, so exhaust is a bit wobbly at the moment... I've sent Dean some measurements however and hopefully he should have a bracket replicated for me soon! But yeah, considering having the mid piece replicated but without the two silencers and just having the backbox so it's not as lairy as a buddyclub. Sounds mint at the moment, however I feel sometimes on warm idle it's slightly quiet, cold idle tho its nice and loud, so much so it seems to piss my neighbour off when I warm it up lol